Field of the Invention
The present invention relates generally to an ejector capable of being preheated, an injection mold including the ejector, and a method of manufacturing an injection-molded part using the injection mold and, more particularly, to an ejector that is able to be preheated, an injection mold whose internal temperature is precisely controlled using the preheated ejector, and a method of manufacturing an injection-molded part using the injection mold.
Description of the Related Art
Generally, during an injection molding process by an injection molding machine, if a temperature of a mold is low, there is a risk of generating defective factors such as increased viscosity, degraded fluidity, incomplete injection of a feedstock into the mold, occurrence of a weld line, a fault in the gloss on a surface of an injection-molded part, or the like. To solve this problem, it is required to increase the temperature of the mold so that the flow resistance and the residual stress of a feedstock are reduced, thereby removing the defective factors of an injection-molded part. In the meantime, after the mold is filled with a feedstock, it is preferred that the mold be rapidly cooled to shorten a cycle of the injection process. Accordingly, a currently available mold needs a temperature regulator to rapidly increase or decrease a temperature of the mold.
A melting point of a binder system in a feedstock for the ceramic injection molding is about 60° C. to 230° C. Therefore, a temperature of a nozzle of an injector containing the feedstock is set to about 70° C. to 250° C. in order to melt the feedstock. If an internal space for injection molding (also referred to as a cavity) in a mold set has low temperature, the feedstock is rapidly solidified during injection, causing an injection-molded part to be defective. To prevent this problem, a temperature of a mold should be set to a proper range according to the melting point of the feedstock. In a conventional ceramic injection molding, however, a temperature of a mold is controlled by a heater installed outside of the mold, so it is difficult to precisely control a temperature of the molding space affecting injection quality of an injection-molded part.